Serving cold food.
Basically the line cook would cook a burger add fries and place it up on the counter. When it got busy sometimes that food would sit there. Then a server would take it and end up bringing it right back to the line cook because: You guessed it, the food was cold.
Networking works in the same way.
When someone hands you their card, introduces you via email, or puts you in touch with someone in person, they are serving you a hot plate that you need to bring to the table.
If you wait for the person to get back to you first, or wait a week or two to respond to that email, or never follow up on that intro, then you are serving cold food. No one wants cold food.
Your best leads are served to you piping hot, it's your job to capitalize on those leads so that you have more satisfied customers. If you don't have time to go into details, a quick "Nice meeting you let's catch up" email goes a long way.
So take the time today to check and see if there are any plates on top of that grill, and if there are...
Get out there and serve them.